The Basic Iterative Method (BIM) [1]} is an advancement of the FGSM. The FGSM is applied iteratively with a small perturbation size. After each iteration the pixel values are clipped to not exceed the perturbation size \(\varepsilon \) . The adversarial example is generated as follows:
\(X_0^{adv} = X,\) 
\(X_{N+1}^{adv} = \text{Clip}_{X,\varepsilon }\lbrace X_N^{adv}-\alpha \mbox{sign}(\nabla _{X}J(X_N^{adv},y_t))\rbrace .\) 
